Grant schrieb: >>> Here is some info on zflashpoint: >>> >>> http://forum.notebookreview.com/showthread.php?p=5163549 >>> >>> It is supposed to be an SSD performance "accelerator". >>> >>> "Gen1 SSDs suffer with small file writes and I read that 90% of >>> Windows writes are small, so that introduces overall system lag. >>> zflashpoint uses a 32MB buffer for small file writes, combining them >>> and dumping them as one big write." >>> >>> Has anyone heard of development of a similar project for Linux? >>> >>> - Grant >>> >> Sounds like laptop-mode to me (app-laptop/laptop-mode-tools). For ext* >> file systems, you can also try the 'commit' mount option. > > On her laptop, I get: > > # cat /proc/sys/vm/laptop_mode > 0 > > There is lots of talk on the internet about the stuttering problems on > SSD netbooks. Are you thinking this problem shouldn't manifest itself > on a Linux system? > > - Grant >
Well, as I see it, there are two distinct problems here: 1. (Cheap) SSDs are slow 2. (Cheap) SSDs are terribly slow on random write Both reasons can produce stuttering and you can't completely fix them. However, you can try to cache random writes until you can commit them as one sequential write. There are several things which will help here: 1. A file system that does not scatter data unnecessarily and which might even align its (meta)data to the erase block boundaries of the SSD.[1] 2. A long commit interval in which writes can be collected until they are actually performed in optimal order(see my last post). 3. A disk scheduler that optimizes for SSD writes instead of HDD writes (like Completely Fair Scheduler on kernel >=2.6.29) 4. An enterprise grade RAID controller 5. An SSD with built-in cache and enough "intelligence" to use it properly I don't see a reason why a Microsoft OS might not make these optimizations if their devs would care about it and I'd really like to see a benchmark between a bleeding edge Linux and a Windows 7 on this topic. Of course, none of these tricks will help with problem 1 and in the end, when your usage pattern provoke it, you will still see stuttering while your system struggles to flush its overly large write caches to the much too slow disk. [1] http://thunk.org/tytso/blog/2009/02/20/aligning-filesystems-to-an-ssds-erase-block-size/
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